Fix vehicle physics?

Hi, I'm trying to learn how to make vehicle physics that works fine for both simulation and arcade type game. I found a opensource one and it's demo is perfect for what I wan't to learn from. Thing is the script is written in Unity4.3, when I try it in unity5 it doesn't behave that way that is should. Not even close. Is there a specific documentation on how to fix it? I never used unity4 before so I don't know the physics difference of the two and how to fix it.

sorry for a bad grammar.

 

Would you mind posting the script?

Maybe it is still using gameObject.rigidbody instead of doing gameObject.GetComponent<RigidBody>() and caching it.

 

This is the code. One of the proble

Code (JavaScript):

1. #pragma strict
2. @script AddComponentMenu("Vehicle/CarControl")
3.  
4. public var Wheel_FL : WheelCollider;
5. public var Wheel_FR : WheelCollider;
6. public var Wheel_RL : WheelCollider;
7. public var Wheel_RR : WheelCollider;
8. public var GearRatio : float[];
9. public var CurrentGear : int = 0;
10. public var EngineTorque : float = 600.0;
11. public var MaxEngineRPM : float = 3000.0;
12. public var MinEngineRPM : float = 1000.0;
13. public var SteerAngle : float = 10;
14. public var controlsEnabled : boolean = false;
15. public var COM : Transform;
16. public var Speed : float;
17. public var maxSpeed : float = 150;
18. public var skidAudio : AudioSource;
19. private var EngineRPM : float = 0.0;
20. private var motorInput : float;
21.  
22. function Start () {
23.     rigidbody.centerOfMass = Vector3(COM.localPosition.x * transform.localScale.x, COM.localPosition.y * transform.localScale.y, COM.localPosition.z * transform.localScale.z);
24. }
25.  
26. function Update () {
27.     Speed = rigidbody.velocity.magnitude * 3.6f;
28.     rigidbody.drag = rigidbody.velocity.magnitude / 100;
29.     EngineRPM = (Wheel_FL.rpm + Wheel_FR.rpm)/2 * GearRatio[CurrentGear];
30.    
31.     ShiftGears();
32.    
33.     //Input For MotorInput.
34.     motorInput = Input.GetAxis("Vertical");
35.    
36.     //Audio
37.     audio.pitch = Mathf.Abs(EngineRPM / MaxEngineRPM) + 1.0;
38.     if (audio.pitch > 2.0) {
39.         audio.pitch = 2.0;
40.     }
41.    
42.     //Is The Car Enabled "Is The Player In The Car"
43.     //If The Player Is In The Car Do These.
44.     if(controlsEnabled){
45.         //Steering
46.         Wheel_FL.steerAngle = SteerAngle * Input.GetAxis("Horizontal");
47.         Wheel_FR.steerAngle = SteerAngle * Input.GetAxis("Horizontal");
48.        
49.         //Speed Limiter / Engine Input.
50.         if(Speed > maxSpeed){
51.             Wheel_FL.motorTorque = 0;
52.             Wheel_FR.motorTorque = 0;
53.         }else{
54.             Wheel_FL.motorTorque = EngineTorque / GearRatio[CurrentGear] * Input.GetAxis("Vertical");
55.             Wheel_FR.motorTorque = EngineTorque / GearRatio[CurrentGear] * Input.GetAxis("Vertical");
56.         }
57.        
58.         //HandBrake
59.         if(Input.GetButtonDown("Jump")){
60.             Wheel_FL.brakeTorque = 100;
61.             Wheel_FR.brakeTorque = 100;
62.         }
63.         if(Input.GetButtonUp("Jump")){
64.             Wheel_FL.brakeTorque = 0;
65.             Wheel_FR.brakeTorque = 0;
66.         }
67.     }
68.    
69.     if(motorInput <= 0){
70.         Wheel_RL.brakeTorque = 30;
71.         Wheel_RR.brakeTorque = 30;
72.     }else if (motorInput >= 0){
73.         Wheel_RL.brakeTorque = 0;
74.         Wheel_RR.brakeTorque = 0;
75.     }
76.    
77.     //SkidAudio.
78.     var CorrespondingGroundHit : WheelHit;
79.     Wheel_RR.GetGroundHit( CorrespondingGroundHit );
80.     if(Mathf.Abs(CorrespondingGroundHit.sidewaysSlip) > 10) {
81.         skidAudio.enabled = true;
82.     }else{
83.         skidAudio.enabled = false;
84.     }
85. }
86.  
87. function ShiftGears() {
88.    
89.     if (EngineRPM >= MaxEngineRPM) {
90.         var AppropriateGear : int = CurrentGear;
91.        
92.         for (var i = 0; i < GearRatio.length; i ++) {
93.             if(Wheel_FL.rpm * GearRatio[i] < MaxEngineRPM) {
94.                 AppropriateGear = i;
95.                 break;
96.             }
97.         }
98.         CurrentGear = AppropriateGear;
99.     }
100.    
101.     if(EngineRPM <= MinEngineRPM) {
102.         AppropriateGear = CurrentGear;
103.         for ( var j = GearRatio.length-1; j >= 0; j -- ) {
104.             if ( Wheel_FL.rpm * GearRatio[j] > MinEngineRPM ) {
105.                 AppropriateGear = j;
106.                 break;
107.             }
108.         }
109.         CurrentGear = AppropriateGear;
110.     }
111. }

I tried modifying the whole code but I just can't get it to feel like I'm driving a vehicle.
You can check the project thread and demo here. http://armedunity.com/topic/6569-vehicle-physics-free-project/
One of the issue was the rear wheels colliders getting drag rather than roll with the vehicle. Other issue I have with it are front wheels acting funny like jittering a bit when idle.

 

The wheel physics system was completely rewritten from Unity 4 to 5. One consequence of this is that code written for the old system probably won't work for the new one.

 

Which makes it hard for me to make a proper car physics. :<

 

There's practically a community novel on this topic.

http://forum.unity3d.com/threads/unity-5-wheelcollider-component-is-unusable.307099/